High-functionality flaxseed protein-polysaccharide natural co-extract with good color and luster as well as preparation method and application of high-functionality flaxseed protein-polysaccharide natural co-extract

Abstract

The invention relates to the field of protein extraction technology and multi-scene application, in particular to a high-functionality flaxseed protein-polysaccharide natural co-extract with good color and luster and a preparation method and application thereof. The method comprises the following steps: performing subcritical extraction on flaxseed cakes, squeezing the flaxseed cakes at low temperature / proper temperature to obtain degreased flaxseed cakes, crushing and screening the degreased flaxseed cakes to obtain degreased flaxseed meal powder, efficiently dissolving out protein and polysaccharide in the flaxseed meal powder through alkali dissolution synchronous double-frequency ultrasonic circulating treatment, and centrifuging to obtain supernate. A membrane separation device and a double-frequency ultrasonic device are connected in series through a pipeline to form a circulating system, obtained protein-polysaccharide supernate is treated through the system, and the protein-polysaccharide supernate is separated through the synergistic effect of key parameters such as membrane molecular size, ultrasonic power and ultrasonic intermittent time. The effect that the protein-polysaccharide supernate is subjected to concentration and intermittent ultrasonic modification at the same time can be achieved, a highly concentrated solution is finally obtained, and the concentrated solution is freeze-dried to obtain the flaxseed protein-polysaccharide natural co-extract. Compared with the existing single high-purity flaxseed protein, the flaxseed protein-polysaccharide co-extract prepared by the method has good color and excellent emulsibility, foamability and gelling property.

Description

Technical Field

[0001] This invention relates to the field of protein extraction technology, specifically to a high-functionality flaxseed protein-polysaccharide natural co-extract with good color, its preparation method, and its application. Background Technology

[0002] Flaxseed cake, a major byproduct of flaxseed oil extraction, is a highly promising natural resource. It is rich in 40%–50% high-quality protein and 30%–40% flaxseed polysaccharides, both of which are functional components with significant development value in food processing and health products, possessing broad prospects for industrial application. However, in the actual extraction and purification process of flaxseed protein, flaxseed polysaccharides have become a core technical bottleneck restricting industrial upgrading. These polysaccharides have extremely strong hydration properties, easily forming a high-viscosity colloidal system upon contact with water. This not only interferes with the isoelectric point sedimentation process of proteins, reducing their solubility and separation efficiency, but also significantly increases the operational difficulty of subsequent processes. Currently, the industry commonly uses wet removal processes to remove flaxseed polysaccharides to mitigate their adverse effects on protein extraction; however, this process suffers from serious resource waste and environmental pollution. More importantly, wet removal damages the natural structure of flaxseed cake, leading to impaired protein and polysaccharide activity, low utilization rates, and difficulty in achieving full value-added processing of the byproduct.

[0003] To further improve the purity and yield of flaxseed protein isolate, researchers have successively explored technologies such as enzyme-assisted extraction and physical field-assisted extraction. However, these methods often have obvious technical shortcomings and cost trade-offs: in pursuit of protein purity, large amounts of water resources and organic solvents are required, or extreme reaction environments of strong acids and alkalis are needed, which not only increases production costs but may also damage the natural functional properties of proteins; at the same time, the high-energy-consuming process conditions are contrary to the current trend of green and low-carbon industrial development.

[0004] Based on this, and considering the natural occurrence and functional characteristics of proteins and polysaccharides in flaxseed meal, a mild synergistic co-extraction process for flaxseed protein and polysaccharides was developed. This process not only avoids the drawbacks of high water consumption, high pollution, and high energy consumption associated with traditional fractional purification processes, but also simultaneously enriches both proteins and polysaccharides, fully preserving their natural structure and synergistic functions. This technological approach has crucial practical significance and application value for realizing the high-value and green utilization of flaxseed meal by-products and promoting the development of the food industry towards resource conservation and environmental friendliness. Summary of the Invention

[0005] In view of this, the present invention provides a high-functionality flaxseed protein-polysaccharide natural co-extract with good color, its preparation method and application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: On the one hand, a method for preparing a high-functionality flaxseed protein-polysaccharide natural co-extract with good color includes the following steps: 1) Disperse the unhulled defatted flaxseed cake in ultrapure water, stir at room temperature, and adjust the pH value with alkali; then, circulate it using dual-frequency synchronous ultrasound, centrifuge, and collect the supernatant; 2) Transfer the supernatant collected in step 1) to the sample chamber of the membrane separation device. While concentrating and purifying the supernatant using membrane separation, perform dual-frequency ultrasonic synchronous circulation treatment to concentrate the supernatant to 20%-50% of its original volume. Then freeze-dry the concentrate to obtain flaxseed protein-polysaccharide co-extract.

[0007] Optionally, the parameters for dual-frequency synchronous ultrasound are: 20 / 40kHz, 55-220W.

[0008] Furthermore, in step 1), the parameters for cyclic processing and assisted extraction using dual-frequency synchronous ultrasound are: pulse holding time 150-900 s, pulse interval time 10 s, and total working time 310-1810 s. In step 2), the parameters for cyclic processing of modified proteins and polysaccharides using dual-frequency synchronous ultrasound are as follows: pulse hold time 150-900 s, pulse interval time 1800 s, and total working time 2100-3600 s.

[0009] It should be noted that the purpose of dual-frequency ultrasonic cyclic treatment is to break down solid-liquid mixtures and promote the dissolution of proteins and polysaccharides in the cake. Compared with traditional single-frequency probe ultrasound, the use of 20 / 40kHz dual-frequency ultrasound can destroy cell structures at different scales, enhance mass transfer efficiency, and improve the dissolution rate of target components.

[0010] A gentle, targeted secondary treatment is performed on the supernatant after centrifugation. This time, the treatment is no longer on a solid-liquid mixture, but rather on a dissolved protein-polysaccharide mixture. By connecting a membrane separation device and a dual-frequency ultrasonic device in series to form a circulating system, the protein-polysaccharide mixture can be concentrated and ultrasonically modified simultaneously. A combination of parameters such as circulating and intermittent ultrasonication, and membrane size, avoids localized overheating and protein denaturation caused by continuous ultrasonication, ensuring treatment effectiveness while maximizing the preservation of the natural activity of biomolecules. Furthermore, the ultrasonication in this step further depolymerizes large aggregates in the concentrate, facilitating continuous concentration. Simultaneously, the microjets and shock waves generated by cavitation drive collisions and interactions between protein and polysaccharide molecules, promoting the formation of more stable and functionally superior natural co-extracts. This step refines the functional properties of the final product.

[0011] Optionally, the pH can be adjusted to 8-10 with alkali.

[0012] Optionally, membrane separation uses MWCO 10-100 kDa membranes.

[0013] The selected membrane pore size range is designed for the molecular weight of the target products (flaxseed protein and polysaccharides). It can simultaneously concentrate proteins and polysaccharides and selectively remove small molecule impurities (such as salts, pigments, monosaccharides, etc.), achieving simultaneous concentration and purification of the target co-extracts.

[0014] Furthermore, the gentle physical sieving mechanism of membrane separation does not disrupt the non-covalent interactions that may exist between proteins and polysaccharides, thus fully preserving the natural state and functional properties of the "co-extract".

[0015] In addition, the "two-step ultrasound" provides the conditions for membrane separation: ultrasound treatment effectively breaks down large particulate impurities, significantly reducing the viscosity of the subsequent supernatant and the risk of particulate blockage, making the membrane separation process more stable, with higher flux and longer membrane life.

[0016] On the other hand, the present invention also claims protection for the application of a flaxseed protein-polysaccharide co-extract prepared by the method described above in the food industry.

[0017] Specifically, the application of the flaxseed protein-polysaccharide co-extract in the field of food ingredients and processing is as follows: a. It can be used as an emulsifier, water-retaining agent and texture improver. When added to meat products, it can improve the water-holding capacity and gel strength of minced meat, reduce the loss of moisture and nutrients during processing, and make the product more firm.

[0018] b. Suitable for yogurt, plant-based milk, dairy beverages, etc. Polysaccharides can improve product stability and delay separation, while proteins can supplement high-quality plant protein and enhance the product's consistency and smooth texture.

[0019] c. Used in bread, biscuits, cakes, etc., protein can strengthen the gluten network of dough, polysaccharides can improve moisture retention, extend product shelf life, and also improve the softness and flavor carrier capacity of baked goods.

[0020] d. Because it is rich in high-quality plant protein and water-soluble polysaccharides, it can be used as a core ingredient to develop meal replacement powders and nutritional supplements, or added to dietary fiber foods to exert a synergistic effect of nutritional supplementation and intestinal health regulation.

[0021] It is worth noting that higher protein purity does not necessarily equate to better functional properties. For example, some plant protein products containing non-protein components may have functional properties equivalent to or even superior to highly purified isolated proteins. Marlies et al. (2017) obtained a blend of soluble protein and polysaccharide from yellow peas through mild co-extraction. Compared with corresponding commercial products, co-extraction preserved the natural protein conformation and synergistically produced positive effects on functional properties with other components. Furthermore, studies have found that flaxseed polysaccharides possess various functions such as thickening, emulsification, gel formation, water retention, anti-oxidation, cholesterol reduction, and blood sugar regulation, and are widely used in food, pharmaceuticals, cosmetics, and environmental materials. Some studies have reported that flaxseed polysaccharides, as a natural water-soluble polysaccharide, help form stable oil-in-water emulsions and have been used to prepare emulsions with flaxseed protein isolate, soy protein isolate, or peanut protein isolate. The resulting flaxseed polysaccharide-protein mixtures or complexes combine the inherent functional properties of both, improve the balance of hydrophilic and hydrophobic structures, and thus regulate their emulsifying abilities.

[0022] Compared with the prior art, the beneficial effects of the present invention are: (1) The innovative co-extraction process simultaneously enriches the protein and polysaccharide functional components in flaxseed cake, avoiding the situation where traditional graded extraction only focuses on a single component and the rest are wasted, maximizing the utilization potential of by-products and realizing efficient recycling of resources.

[0023] (2) By connecting the membrane separation device and the dual-frequency ultrasonic device in series to form a circulation system, the dual-frequency ultrasonic and membrane separation are used simultaneously to achieve effective enrichment of protein and polysaccharide while completing green modification. This avoids the drawbacks of high water consumption and high pollution of traditional wet degumming, and solves the problems of high energy consumption and component damage of chemical-assisted extraction, which is more in line with the green and low-carbon industrial development trend.

[0024] (3) The co-extract retains the synergistic mechanism of flaxseed protein and polysaccharide. Compared with single high-purity flaxseed protein and traditional extracts, it not only has good color (avoiding oxidation of components during extraction), but also significantly improves core functional characteristics such as emulsification, foaming and gelation through the synergistic effect of the two. It can be flexibly applied to food systems such as meat products, dairy products, baked goods, and beverages. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the preparation process of flaxseed protein-polysaccharide natural co-extract.

[0027] Figure 2 The appearance of the products in Examples 1-9 and the comparative examples is shown.

[0028] Figure 3 The gelation effect of Examples 1-9 and comparative products is shown. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0031] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0032] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0033] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0034] This invention discloses a method for preparing a high-functionality flaxseed protein-polysaccharide natural co-extract with good color.

[0035] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0036] Example 1: First, unhulled flaxseed cake, pressed at low / moderate temperature, was subjected to subcritical extraction to obtain defatted flaxseed cake. This was then pulverized and sieved using a fully automated hammer mill (equipped with a 0.5 mm cyclone mill screen) to obtain defatted flaxseed meal powder. Next, the unhulled defatted flaxseed meal was dispersed in ultrapure water at a ratio of 1:20 (w / v) and stirred at room temperature (25℃) for 1 hour, with the pH adjusted to 9.0 using NaOH. Then, it was circulated using dual-frequency synchronous ultrasound (20 kHz: 110 W, 40 kHz: 110 W), with a pulse duration of 300 s, a pulse interval of 10 s, and a total processing time of 610 s. Finally, the mixture was centrifuged at 6000 g for 30 min, and the supernatant was collected. The supernatant was transferred to the sample chamber of a membrane separation device. Simultaneously, the supernatant was concentrated and purified using a membrane separation system (MWCO 100 kDa Hydrosart® membrane) at a flow rate of 120 mL / min, while undergoing simultaneous dual-frequency ultrasonic synchronous circulation (20 kHz: 110 W, 40 kHz: 110 W, pulse hold time 300 s, pulse interval 1800 s, total working time 2400 s), concentrating it to approximately 20% of its total volume. The resulting solution was then freeze-dried to obtain flaxseed protein-polysaccharide co-extract 1.

[0037] Example 2: First, unhulled flaxseed cake, pressed at low / moderate temperature, was subjected to subcritical extraction to obtain defatted flaxseed cake. This was then pulverized and sieved using a fully automated hammer mill (equipped with a 0.5 mm cyclone mill screen) to obtain defatted flaxseed meal powder. Next, the unhulled defatted flaxseed meal was dispersed in ultrapure water at a ratio of 1:20 (w / v) and stirred at room temperature (25°C) for 1 hour, with the pH adjusted to 9.0 using NaOH. Then, it was circulated using dual-frequency synchronous ultrasound (20 kHz: 55 W, 40 kHz: 55 W), with a pulse duration of 900 s, a pulse interval of 10 s, and a total processing time of 1810 s. Finally, the mixture was centrifuged at 6000 g for 30 min, and the supernatant was collected. The supernatant was transferred to the sample chamber of a membrane separation device. Simultaneously, the supernatant was concentrated and purified using a membrane separation system (MWCO 100 kDa Hydrosart® membrane) at a flow rate of 120 mL / min, while undergoing simultaneous dual-frequency ultrasonic synchronous circulation (20 kHz: 55 W, 40 kHz: 55 W, pulse hold time 900 s, pulse interval time 1800 s, total working time 3600 s), concentrating it to approximately 20% of its total volume. The resulting solution was then freeze-dried to obtain flaxseed protein-polysaccharide co-extract 2.

[0038] Example 3: First, unhulled flaxseed cake, pressed at low / moderate temperature, is subjected to subcritical extraction to obtain defatted flaxseed cake. This is then pulverized and sieved using a fully automated hammer mill (equipped with a 0.5 mm cyclone mill screen) to obtain defatted flaxseed meal powder. Next, the unhulled defatted flaxseed meal is dispersed in ultrapure water at a ratio of 1:20 (w / v) and stirred at room temperature (25℃) for 1 hour, with the pH adjusted to 9.0 using NaOH. Then, it is circulated using dual-frequency synchronous ultrasound (20 kHz: 220 W, 40 kHz: 220 W), with a pulse duration of 150 s, a pulse interval of 10 s, and a total processing time of 310 s. Finally, the mixture is centrifuged at 6000 g for 30 min, and the supernatant is collected. The supernatant was transferred to the sample chamber of a membrane separation device. While the supernatant was concentrated and purified using membrane separation (MWCO 100 kDa Hydrosart® membrane) (flow rate: 120 mL / min), it was simultaneously subjected to dual-frequency ultrasonic synchronous circulation treatment (20 kHz: 220 W, 40 kHz: 220 W, pulse hold time 150 s, pulse interval time 1800 s, total working time 2100 s). The solution was concentrated to approximately 50% of its total volume. The resulting solution was then freeze-dried to obtain flaxseed protein-polysaccharide co-extract 3.

[0039] Example 4: First, unhulled flaxseed cake, pressed at low / suitable temperature, was subjected to subcritical extraction to obtain defatted flaxseed cake. This was then pulverized and sieved using a fully automated hammer mill (equipped with a 0.5 mm cyclone mill screen) to obtain defatted flaxseed meal powder. Next, the unhulled defatted flaxseed meal was dispersed in ultrapure water at a ratio of 1:20 (w / v) and stirred at room temperature (25°C) for 1 hour, with the pH adjusted to 9.0 using NaOH. Then, it was circulated using dual-frequency synchronous ultrasound (20 kHz: 220 W, 40 kHz: 110 W), with a pulse duration of 300 s, a pulse interval of 10 s, and a total processing time of 610 s. Finally, the mixture was centrifuged at 6000 g for 30 min, and the supernatant was collected. The supernatant was transferred to the sample chamber of a membrane separation device. Simultaneously, the supernatant was concentrated and purified using a membrane separation system (MWCO 100 kDa Hydrosart® membrane) at a flow rate of 120 mL / min, while undergoing simultaneous dual-frequency ultrasonic synchronous circulation (20 kHz: 110 W, 40 kHz: 110 W, pulse hold time 300 s, pulse interval 1800 s, total working time 2400 s), concentrating it to approximately 50% of its total volume. The resulting solution was then freeze-dried to obtain flaxseed protein-polysaccharide co-extract 4.

[0040] Example 5: First, unhulled flaxseed cake, pressed at low / moderate temperature, was subjected to subcritical extraction to obtain defatted flaxseed cake. This was then pulverized and sieved using a fully automated hammer mill (equipped with a 0.5 mm cyclone mill screen) to obtain defatted flaxseed meal powder. Next, the unhulled defatted flaxseed meal was dispersed in ultrapure water at a ratio of 1:20 (w / v) and stirred at room temperature (25°C) for 1 hour, with the pH adjusted to 8.0 using NaOH. Then, it was circulated using dual-frequency synchronous ultrasound (20 kHz: 110 W, 40 kHz: 110 W), with a pulse duration of 300 s, a pulse interval of 10 s, and a total processing time of 610 s. Finally, the mixture was centrifuged at 6000 g for 30 min, and the supernatant was collected. The supernatant was transferred to the sample chamber of a membrane separation device. Simultaneously, the supernatant was concentrated and purified using a membrane separation system (MWCO 50 kDa Hydrosart® membrane) at a flow rate of 120 mL / min, while undergoing simultaneous dual-frequency ultrasonic synchronous circulation (20 kHz: 110 W, 40 kHz: 110 W, pulse hold time 300 s, pulse interval 1800 s, total working time 2400 s), concentrating it to approximately 30% of its total volume. The resulting solution was then freeze-dried to obtain flaxseed protein-polysaccharide co-extract 5.

[0041] Example 6: First, unhulled flaxseed cake, pressed at low / moderate temperature, was subjected to subcritical extraction to obtain defatted flaxseed cake. This was then pulverized and sieved using a fully automated hammer mill (equipped with a 0.5 mm cyclone mill screen) to obtain defatted flaxseed meal powder. Next, the unhulled defatted flaxseed meal was dispersed in ultrapure water at a ratio of 1:20 (w / v) and stirred at room temperature (25°C) for 1 hour, with the pH adjusted to 10.0 using NaOH. Then, it was circulated using dual-frequency synchronous ultrasound (20 kHz: 110 W, 40 kHz: 110 W), with a pulse duration of 300 s, a pulse interval of 10 s, and a total processing time of 610 s. Finally, the mixture was centrifuged at 6000 g for 30 min, and the supernatant was collected. The supernatant was transferred to the sample chamber of a membrane separation device. Simultaneously, dual-frequency ultrasonic synchronous circulation (20 kHz: 110 W, 40 kHz: 110 W, pulse hold time 300 s, pulse interval 1800 s, total working time 2400 s) was performed to concentrate the supernatant to approximately 30% of its total volume. The resulting solution was then freeze-dried to obtain flaxseed protein-polysaccharide co-extract 6.

[0042] Example 7: First, unhulled flaxseed cake, pressed at low / moderate temperature, was subjected to subcritical extraction to obtain defatted flaxseed cake. This was then pulverized and sieved using a fully automated hammer mill (equipped with a 0.5 mm cyclone mill screen) to obtain defatted flaxseed meal powder. Next, the unhulled defatted flaxseed meal was dispersed in ultrapure water at a ratio of 1:20 (w / v) and stirred at room temperature (25℃) for 1 hour, with the pH adjusted to 9.0 using NaOH. Then, it was circulated using dual-frequency synchronous ultrasound (20 kHz: 110 W, 40 kHz: 110 W), with a pulse duration of 300 s, a pulse interval of 10 s, and a total processing time of 610 s. Finally, the mixture was centrifuged at 6000 g for 30 min, and the supernatant was collected. The supernatant was transferred to the sample chamber of a membrane separation device. Simultaneously, the supernatant was concentrated and purified using a membrane separation system (MWCO 30 kDa Hydrosart® membrane) at a flow rate of 120 mL / min, while undergoing simultaneous dual-frequency ultrasonic synchronous circulation (20 kHz: 110 W, 40 kHz: 110 W, pulse hold time 300 s, pulse interval 1800 s, total working time 2400 s), concentrating it to approximately 50% of its total volume. The resulting solution was then freeze-dried to obtain flaxseed protein-polysaccharide co-extract 7.

[0043] Example 8: First, unhulled flaxseed cake, pressed at low / moderate temperature, was subjected to subcritical extraction to obtain defatted flaxseed cake. This was then pulverized and sieved using a fully automated hammer mill (equipped with a 0.5 mm cyclone mill screen) to obtain defatted flaxseed meal powder. Next, the unhulled defatted flaxseed meal was dispersed in ultrapure water at a ratio of 1:20 (w / v) and stirred at room temperature (25℃) for 1 hour, with the pH adjusted to 9.0 using NaOH. Then, it was circulated using dual-frequency synchronous ultrasound (20 kHz: 220 W, 40 kHz: 220 W), with a pulse duration of 600 s, a pulse interval of 10 s, and a total processing time of 1210 s. Finally, the mixture was centrifuged at 6000 g for 30 min, and the supernatant was collected. The supernatant was transferred to the sample chamber of a membrane separation device. Simultaneously, dual-frequency ultrasonic synchronous circulation (20 kHz: 220 W, 40 kHz: 220 W, pulse hold time 600 s, pulse interval 1800 s, total working time 3000 s) was performed to concentrate the supernatant to approximately 20% of its total volume. The resulting solution was then freeze-dried to obtain flaxseed protein-polysaccharide co-extract 8.

[0044] Example 9: First, unhulled flaxseed cake, pressed at low / moderate temperature, was subjected to subcritical extraction to obtain defatted flaxseed cake. This was then pulverized and sieved using a fully automated hammer mill (equipped with a 0.5 mm cyclone mill screen) to obtain defatted flaxseed meal powder. Next, the unhulled defatted flaxseed meal was dispersed in ultrapure water at a ratio of 1:20 (w / v) and stirred at room temperature (25℃) for 1 hour, with the pH adjusted to 9.0 using NaOH. Then, it was circulated using dual-frequency synchronous ultrasound (20 kHz: 110 W, 40 kHz: 110 W), with a pulse duration of 600 s, a pulse interval of 10 s, and a total working time of 1210 s. Finally, the mixture was centrifuged at 6000 g for 30 min, and the supernatant was collected. The supernatant was transferred to the sample chamber of a membrane separation device. Simultaneously, dual-frequency ultrasonic synchronous circulation (20 kHz: 110 W, 40 kHz: 110 W, pulse hold time 600 s, pulse interval time 1800 s, total working time 3000 s) was performed to concentrate the supernatant to approximately 50% of its total volume. The resulting solution was then freeze-dried to obtain flaxseed protein-polysaccharide co-extract 9.

[0045] To further demonstrate the beneficial effects of the present invention and to better understand it, the technical features disclosed in the present invention are further illustrated by the following comparative examples and test cases, but these should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above-described invention, without inventive effort, are also considered to fall within the protection scope of the present invention.

[0046] Comparative Example 1: First, defatted flaxseed cake, obtained from low-temperature / temperature-pressed flaxseed cake, was subjected to subcritical extraction to obtain defatted flaxseed cake. This cake was then pulverized and sieved using an automated hammer mill (equipped with a 0.5 mm cyclone mill screen) to obtain defatted flaxseed meal powder. Next, the defatted flaxseed meal was dispersed in ultrapure water at a ratio of 1:20 (w / v) and stirred at room temperature (25°C) for 2 hours. The pH was adjusted to 9.0 with 2 M NaOH. The mixture was then centrifuged at 6000 g for 30 min to remove insoluble impurities, and the supernatant was collected. Subsequently, the pH was adjusted to 4.2. The mixture was centrifuged again under the same conditions, and the precipitate was collected and reconstituted in ultrapure water at pH 7.0 at a ratio of 1:5 (w / v). Finally, the resulting solution was freeze-dried to obtain flaxseed protein isolate (AE-FPI).

[0047] Taking the flaxseed protein-polysaccharide co-extracts and flaxseed protein isolates obtained in Examples 1-9 and Comparative Example 1 as examples, the macroscopic appearance, color analysis, protein content, polysaccharide content, total yield, solubility, emulsifying properties and emulsification stability, foaming properties and foam stability, and gelling properties of the products obtained by different methods were studied.

[0048] 1. Protein content determination The protein content of the examples and comparative examples was determined by the Kjeldahl method, and the nitrogen conversion coefficient was determined in accordance with the national standard GB5009.5-2016.

[0049] 2. Method for determining total sugar content Protein concentration was determined using a total sugar content assay kit (Beijing Box Biotechnology Co., Ltd.) 3. Method for determining total extraction rate

[0050] 4. Appearance and color measurement Weigh an appropriate amount of sample powder and spread it evenly in a transparent circular container. Use a digital camera to photograph its appearance. Select three different locations and measure the colorimetric value of the sample using a handheld colorimeter. The sample's brightness value (L*), red / green value (+a* / -a*), and yellow / blue value (+b* / -b*) are represented. The whiteness value of the protein sample is calculated using the following formula.

[0051]

[0052] 5. Solubility determination Prepare a 1% (w / v) protein solution with pH 7.0. Dilute the sample with ultrapure water to a 0.1% (w / v) test solution and centrifuge at 4000 g for 10 min. Collect the supernatant after centrifugation and determine the protein concentration using bovine serum albumin (BSA) as the standard protein and a BCA protein concentration assay kit (Beijing Lanjieke Technology Co., Ltd.).

[0053]

[0054] 6. Determination of emulsifying properties and emulsion stability Prepare a 1% (w / v) protein solution at pH 7.0. Mix 15 mL of the sample solution with 5 mL of flaxseed oil at 13400 rpm for 2 min to homogenize. Take 50 μL of the freshly prepared emulsion and mix it with 5 mL of 0.1% SDS. Measure the absorbance at 500 nm and record it as A0. Let it stand at room temperature for 10 min, and measure the absorbance at 500 nm again, recording it as A0. 10 The formulas for calculating emulsifying property (EAI) and emulsifying stability (ESI) are as follows:

[0055]

[0056] In the formula, EAI is the Emulsification Index (EAI), ESI is the Emulsification Stability Index (ESI), DF is the dilution factor, C is the sample concentration (g / mL), and θ is the oil volume fraction. T = 10 min, ΔA is the difference between A0 and A 10 difference.

[0057] 7. Determination of foaming properties and foam stability Prepare a 1% (w / v) sample solution with pH 7.0. Take 15 mL of the sample solution into a specially designed cylindrical glass dish and stir at 13400 rpm for 2 min using an IKA high-speed homogenizer. After stirring, measure the foam height at 2 min and 60 min using a ruler, and record them as V2 and V, respectively. 60 Calculate foaming property (FA) and foam stability (FS).

[0058]

[0059]

[0060] In the formula, FA is the foaming index, FS is the foam stability index, V2 is the foam volume in 2 minutes, and V 60 It is the foam volume after 60 minutes.

[0061] 8. Gelation test Sample solutions with concentrations of 1%, 3%, 5%, 7%, and 10% were prepared. The sample dispersions in the test tubes were heated in a water bath at 95°C for 30 min, immediately cooled in an ice-water bath, and stored at 4°C for about 24 h. Then, they were taken out and photographed for observation.

[0062] Depend on Figure 2As shown in Table 1, the comparative examples generally exhibit a darker yellowish-brown color, with a b* value as high as 37.64, significantly higher than all other examples. Examples 1-9 exhibit a light white / brown color scheme, with variations in color depth among the different examples. However, the whiteness values ​​(WI) of the products from Examples 1-9 are all above 59, significantly higher than the comparative examples (~57). This is mainly attributed to the gentler alkaline-coated membrane separation process, which eliminates the need for strong acid-base adjustment and effectively avoids the co-precipitation of plant pigments and small molecule impurities during the acid precipitation step, resulting in better whiteness (WI) of the product (e.g., WI=71.48 in Example 5). Furthermore, visual observation revealed that the texture of the comparative examples was relatively uneven, while the powder of Examples 1, 2, 3, 5, and 8 was more uniform and fine. This also indicates that the flaxseed protein-polysaccharide co-extract prepared by this patent has better color (higher whiteness value), significantly superior to single flaxseed protein isolate prepared by traditional methods, which is beneficial for broadening the application prospects of flaxseed protein.

[0063] Table 1 Color analysis of Examples 1-9 and comparative products

[0064] Analysis of the results in Table 2 shows that Examples 1-9 prepared by the method of the present invention successfully achieved effective simultaneous enrichment of flaxseed protein and polysaccharides. The protein content of Examples 1-9 was 52.82%~60.10%, the polysaccharide content was 24.41%~28.93%, and the total content of the two reached 77.46% (Example 5)~85.77% (Example 8), achieving preferential recovery of the dual-functional components.

[0065] Compared to the traditional alkali dissolution and acid precipitation process (Comparative Example 1), which can only achieve high-purity enrichment of a single protein (protein content of 94.21% and polysaccharide content of only 2.60% as residual impurities), this process is limited to protein extraction and is restricted by protein solubility. In contrast, the process of this invention covers the extraction of both proteins and polysaccharides, expanding the recovery range of effective components from the raw materials and breaking through the limitations of traditional single-component purification. While achieving simultaneous enrichment of dual-functional components, it can also achieve better extraction efficiency, demonstrating significant technological innovation and application value.

[0066] Table 2. Protein content, polysaccharide content, and total protein and polysaccharide content of Examples 1-9 and comparative products.

[0067] Analysis of the results in Table 3 shows that the solubility of the comparative example was significantly lower than that of all the examples (31.60% vs. 46.60%-53.57%), while the solubility of the examples was generally around 50%, indicating a significant overall improvement. This is mainly because the membrane separation process is gentler (requiring no drastic pH changes or precipitation operations), which can prevent protein aggregation by preserving the native conformation or soluble structure of the protein, and can also prevent the aggregation between protein molecules by inducing steric hindrance through co-enrichment of polysaccharides, thereby improving the solubility of the product. The high solubility of the examples is more suitable for the needs of the food and pharmaceutical industries, such as for use in liquid formulations like beverages and oral liquids.

[0068] Table 3 Solubility of Examples 1-9 and Comparative Example Products

[0069] As shown in Table 4, the emulsifying performance of the comparative examples was significantly weaker than that of Examples 1-9. The EAI of the comparative examples was only 6.77 m² / g, and the ESI was 93.75 min; while the EAI of the examples generally increased to 7.30~8.88 m² / g, and the highest ESI reached 245.02 min, indicating superior overall emulsifying ability and stability. In summary, the natural co-extraction process of flaxseed protein and polysaccharides in this invention achieves significant optimization of the product's emulsifying performance through "preserving protein activity + introducing polysaccharide synergy," a characteristic that gives it greater application potential in emulsion-type foods (such as vegetable fat cream and salad dressing) or cosmetics.

[0070] Table 4. Emulsifying properties and emulsion stability of Examples 1-9 and comparative products

[0071] As shown in Table 5, the FC of the comparative example was 161.48%; while the FC of Examples 1-9 was significantly improved to 220.55%~284.42%, which is better than the comparative example overall, with an improvement of at least 17.6%. This characteristic makes it more suitable for scenarios that require high foaming efficiency, such as pastry whipping.

[0072] Table 5. Foaming properties (FC) of Examples 1-9 and Comparative Examples

[0073] Depend on Figure 3It is evident that the comparative product, primarily composed of denatured and aggregated high-purity proteins, lacks flexible intermolecular interaction sites and lacks the synergistic cross-linking of polysaccharides, thus failing to form an effective gel at concentrations between 1% and 10%. In contrast, the products of Examples 1-3 are protein-polysaccharide mixtures, where soluble proteins retain more flexible binding sites such as hydrogen bonds and hydrophobic interactions. Simultaneously, polysaccharides act as "cross-linking bridges" connecting protein molecules. At a concentration of 3%, the interactions between the protein and polysaccharide co-extracts have begun to construct a loose network structure (showing a gelation tendency). When the concentration increases to 5%, intermolecular interactions are further enhanced, forming a stable three-dimensional network, thereby achieving effective gel formation. This result demonstrates the advantage of the present invention's process in synergistically endowing the product with gelation function through the synergistic interaction of flaxseed protein and polysaccharide components, while the traditional alkali-dissolving and acid-precipitating process loses its good gelation ability due to the denaturation of a single component and protein.

[0074] This invention utilizes a "cyclic + intermittent combined ultrasonic synchronous membrane separation process" to prepare a natural co-extract of flaxseed protein and polysaccharides. Compared to the traditional "alkali dissolution and acid precipitation" process for isolated flaxseed protein, this invention offers several advantages: In terms of composition and appearance, it achieves effective synergistic enrichment of flaxseed protein and polysaccharides, resulting in a more uniform appearance and better whiteness; in terms of physicochemical properties, it significantly improves solubility, exhibiting a gelation tendency at 3% concentration and forming a stable gel at 5% (compared to no effective gel in the control group); in terms of functional properties, it demonstrates superior emulsifying activity, emulsifying stability, and foaming properties, and its functions can be optimized through component control. In summary, this invention's process preserves the soluble conformation of the protein while simultaneously enriching the polysaccharides, making it more industrially valuable than alkali dissolution and acid precipitation in terms of product functional diversity and application adaptability.

[0075] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A process for the preparation of high functional flaxseed protein-polysaccharide natural co-extract with good colour shade, characterized by, The method comprises the following steps: The low-temperature / temperate-temperature pressed flaxseed cake is subjected to subcritical extraction to obtain defatted flaxseed cake, which is further crushed and sieved to obtain defatted flaxseed meal powder; 1) The unhusked defatted flaxseed meal powder is dispersed in ultrapure water, stirred at room temperature, and the pH value is adjusted with alkali; then, the double-frequency ultrasonic is used for cyclic treatment, centrifugation, and collection of supernatant; 2) The membrane separation device and the double-frequency ultrasonic device are connected through pipelines to form a circulation system, and then the supernatant collected in step 1) is transferred to the sample chamber of the membrane separation device, and the supernatant is concentrated and purified by membrane separation while being treated by double-frequency ultrasonic, that is, intermittent ultrasonic treatment while concentrating, when the supernatant is concentrated to 20%-50% of the original volume, the concentrated liquid is freeze-dried to obtain flaxseed protein-polysaccharide co-extract.

2. The production method according to claim 1, characterized by, The parameters of the double-frequency synchronous ultrasonic are: 20 / 40 kHz, 55-220 W.

3. The production method according to claim 1 or 2, characterized by, In step 1), the parameters of the double-frequency ultrasonic for cyclic treatment assisted extraction are: the pulse holding time is set to 150-900 s, the pulse interval time is 10 s, and the total working time is 310-1810 s; In step 2), the parameters of the double-frequency ultrasonic for cyclic treatment of protein and polysaccharide modification are: the pulse holding time is set to 150-900 s, the pulse interval time is 1800 s, and the total working time is 2100-3600 s.

4. The method of claim 1, wherein, The alkali-adjusted pH value is 8-10.

5. The preparation method according to claim 1, characterized in that, The membrane separation uses a membrane with MWCO of 10-100 KDa.

6. A flaxseed protein-polysaccharide co-extract prepared according to the method of claim 1, characterized in that, The flaxseed protein-polysaccharide co-extract is a high-functionality flaxseed protein-polysaccharide natural co-extract with good color.

7. The application of the flaxseed protein-polysaccharide co-extract prepared by the method of claim 1 in the food industry.

8. Use according to claim 7, characterized in that, The application of the flaxseed protein-polysaccharide co-extract in food ingredients.

9. Use according to claim 7, characterized in that, The application of the flaxseed protein-polysaccharide co-extract in food processing.

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